i. Field of the Invention:
This invention relates to a novel metal-working oil composition, and more particularly to a metal-working oil composition containing a lube-oil component, a specific water-soluble polymer and a surfactant, and optionally in combination with an extreme-pressure additive.
ii. Description of the Prior Art:
Conventional metal-working oils which have generally been used are each obtained by adding lube-oil additives such as an oilness agent, extreme-pressure additve, rust preventive and/or antioxidant to a lube-oil component such as an oil and fat, mineral oil or fatty acid ester and then converting the resultant mixture into an o/w-type emulsion by means of an emulsifier. They are fed to metal-working parts, usually with concentrations of 1 to 20%. In the case of rolling a metal for example, it has however been attempted to increase, namely, speed up the rolling speed so as to achieve mass production, relying upon rapid advancement in rolling facilities and technology which has been achieved in recent years. Reflecting such an attempt, requirements for rolling mill oil such as lubricity, circulation stability, working efficiency and treatment readiness of waste water have become progressively severer. There is thus a strong standing desire for the development of a rolling mill oil which can satisfactorily meet such requirements. However, conventional rolling mill oils which make use of emulsifier are accompanied by various drawbacks and are hence unable to fulfill such requirements. In the case of a conventional rolling mill oil relying upon an emulsifier, the rolling lubricity was controlled by changing the type and amount of the emulsifier in such a way that the amount of the oil which was to adhere on rollers and each workpiece, in other words, the plate-out quantity was either increased or decreased. In such an emulsifier-containing rolling mill oil as described above, there was a problem that the plate-out quantity and the circulation stability of the emulsion showed mutually-contradictory tendency, namely, the plate-out quantity to each workpiece is decreased and the lubricity is thus rendered insufficient if the stability of the emulsion is enhanced. If one tried to increase the plate-out quantity, the emulsion became unstable and developed various problems when circulated for its reuse. Accordingly, conventional rolling mill oils making use of emulsifiers were accompanied by such drawbacks as mentioned above. Forthermore, still further improvements are also desired to the lubricity and working efficiency of other metal-working oils such as press-working oils and cutting oils.
The present inventors therefore carried out a research with a view toward solving the aforementioned drawbacks which conventional emulsion-type metal working-oil had. As a result, it was succeeded to improve the above-described drawbacks by using a lube-oil component, which contained an oil and fat or wax having a melting point of 20.degree. to 100.degree. C., in combination with a specific hydrophilic dispersant (a water-soluble, anionic, polymer compound) in such a way that the lube-oil component was stably suspended and dispersed in a solid form in water at a temperature below the melting point but the resultant dispersion became unstable when fed to each working part, i.e., at a temperature above the melting point. A patent application has been already made on the above finding (see, Japanese patent application Laid-open No. 147593/1980).